Effect of the anodization voltage on the porewidening rate of nanoporous anodic alumina

A detailed study of the pore-widening rate of nanoporous anodic alumina layers as a function of the anodization voltage was carried out. The study focuses on samples produced under the same electrolyte and concentration but different anodization voltages within the self-ordering regime. By means of ellipsometry-based optical characterization, it is shown that in the porewidening process, the porosity increases at a faster rate for lower anodization voltages. This opens the possibility of obtaining three-dimensional nanostructured nanoporous anodic alumina with controlled thickness and refractive index of each layer, and with a refractive index difference of up to 0.24 between layers, for samples produced with oxalic acid electrolytes

Echinoderms from the Museum of Zoology from the Universidad de Costa Rica

El Museo de Zoología de la Universidad de Costa Rica (MZUCR) se funda en 1966 y alberga la colección de organismos vertebrados e invertebrados más completa de Costa Rica. El MZUCR cuenta actualmente con 24 colec-ciones que contienen más de cinco millones de especíme-nes, y más de 13 000 especies identificadas. Las primeras colecciones datan 1960 e incluyen peces, reptiles, anfibios, poliquetos, crustáceos y equinodermos. Para este último grupo, el MZUCR posee un total de 157 especies, en 1 173 lotes y 4 316 ejemplares. Estas 157 especies representan el 54% del total de especies de equinodermos que posee Costa Rica (293 especies). El resto de especies están repar-tidas en las siguientes instituciones: Academia de la Cien-cias de California (CAS) (4.8%), Instituto Oceanográfico Scripps (SIO) (5.2%), en la Colección Nacional de equino-dermos “Dra. Ma. Elena Caso” de la Universidad Nacional Autónoma de México (ICML-UNAM) (12.7%), Museo de Zoología Comparada de Harvard (MZC) (19.2%), y en el Museo Nacional de Historia Natural del Instituto Smithso-niano (USNM) (35.1%). Es posible que haya material de Costa Rica en el Museo de Historia Natural de Dinamarca (NCD) y en el Museo de Historia Natural de los Ángeles (LACM), sin embargo, no hubo acceso a dichas coleccio-nes. A su vez hay 9.6% de especies que no aparecen en ningún museo, pero están reportadas en la literatura. Con base en esta revisión de colecciones se actualizó el listado taxonómico de equinodermos para Costa Rica que consta de 293 especies, 152 géneros, 75 familias, 30 órdenes y cinco clases. La costa Pacífica de Costa Rica posee 153 especies, seguida por la isla del Coco con 134 y la costa Caribe con 65. Holothuria resultó ser el género más rico con 25 especies.The Museum of Zoology, Universidad de Costa Rica (MZUCR) was founded in 1966 and houses the most complete collection of vertebrates and invertebrates in Costa Rica. The MZUCR currently has 24 collections containing more than five million specimens, and more than 13 000 species. The earliest collections date back to 1960 and include fishes, reptiles, amphibians, polychaetes, crustaceans and echinoderms. For the latter group, the MZUCR has a total of 157 species, in 1 173 lots and 4 316 specimens. These 157 species represent 54% of the total species of echino-derms from Costa Rica. The remaining species are distributed in the following institutions: California Academy of Sciences (CAS) (4.8%), Scripps Oceanographic Institute (SIO) (5.2%), National Echinoderm Collection “Dr. Ma. Elena Caso” from the National Autonomous University of Mexico (ICML-UNAM) (12.7%), the National Museum of Natural History, Smithsonian Institute (USNM) (35.1%), and the Harvard Museum of Comparative Zoology (19.2%). There may be material from Costa Rica in the Natural History Museum of Denmark (NCD) and the Natural History Museum of Los Angeles (LACM), however, there was no access to such collections. There are 9.6% that do not appear in museums, but are reported in the literature. Based on this revision, the taxonomic list of echinoderms for Costa Rica is updated to 293 species, 152 genera, 75 families, 30 orders and 5 classes. The Pacific coast of Costa Rica has 153 species, followed by the Isla del Coco with 134 and the Caribbean coast with 65. Holothuria is the most diverse genus with 25 species.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de BiologíaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Artes y Letras::Museo de la Universidad de Costa Ric

Photonic stop bands in quasi-random nanoporous anodic alumina structures

The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic alumina structures is investigated by means of rigorous 2D finite-difference time-domain calculations. Self-assembled porous anodic alumina shows a random distribution of domains, each of them with a very definite triangular pattern, constituting a quasi-random structure. The observed stop bands are similar to those of photonic quasicrystals or random structures. As the pores of nanoporous anodic alumina can be infiltrated with noble metals, nonlinear or active media, it makes this material very attractive and cost-effective for applications including inhibition of spontaneous emission, random lasing, LEDs and biosensors

Advances in Optical Biosensors and Sensors Using Nanoporous Anodic Alumina

This review paper focuses on recent progress in optical biosensors using self-ordered nanoporous anodic alumina. We present the fabrication of self-ordered nanoporous anodic alumina, surface functionalization, and optical sensor applications. We show that self-ordered nanoporous anodic alumina has good potential for use in the fabrication of antibody-based (immunosensor), aptamer-based (aptasensor), gene-based (genosensor), peptide-based, and enzyme-based optical biosensors. The fabricated optical biosensors presented high sensitivity and selectivity. In addition, we also showed that the performance of the biosensors and the self-ordered nanoporous anodic alumina can be used for assessing biomolecules, heavy ions, and gas molecules

Fabrication and characterization of high-density arrays of P3HT nanopillars on ITO/glass substrates

High-density arrays of semiconducting Poly(3-hexylthiophene) nanopillars are fabricated on indiumtin-oxide/glass substrates by replicating from nanoporous anodic alumina via spin-coating and melt-assisted wetting methods. The geometry of the resulting nanostructure, which is analyzed in detail through environmental scanning electron microscopy, presents an average nanopillar height of 300 nm and an average distance between adjacent nanopillars of 50 nm. In order to check if the fabricated nanopillars are entirely solid without any entrapped gas bubbles, cross-sectional transmission electron microscopy is performed. The current density-voltage characteristic of these arrays is characterized by current sensing atomic force microscopy. Results show higher conductivity than thin films of the same polymer. It is demonstrated that there is nanoconfinement of polymer chains into the pores during the template-assisted process by means of p-X-ray diffraction. This implies a high alignment of such chains into the nanopillars bulk and, thus, an increasing of conductivity. It is expected that this nanostructure will have multiple potential applications such as organic bulk-heterojunction solar cells, sensors, optoelectronic devices, etc

Calculation of angular-dependent reflectance and polarimetry spectra of nanoporous anodic alumina-based photonic crystal slabs

International audienc

Photonic band measurement by angle-resolved spectroscopy and polarimetry

International audienc

Interplay Between Morphology, Optical Properties, and Electronic Structure of Solution-Processed Bi₂S₃ Colloidal Nanocrystals

Bi₂S₃ nanocrystals with different shapes and sizes are obtained by a hot injection approach using bismuth neodecanoate and thiolamine as bismuth and sulfur precursors. The colloid morphology, from nanodots to nanorods, with sizes ranging from 3–4 nm to 40–50 nm strongly depends on the preparation conditions such as injection temperature and ratio of Bi/S precursors and ultimately impacts the optical and electrical properties of the final nanocrystals. The resulting products are analyzed using X-ray powder diffraction (XRD), transmission electron microscope (TEM), UV–vis absorption spectroscopy, and photoluminescence spectroscopy (PL). A blue shift in the band gap is observed at 1.87, 1.89, and 2.04 eV as we go from nanodots to nanorods with aspect ratios of 3, 5, and 1, respectively. These observations indicate quantum confinement effects due to the different diameters of nanocrystals. The crystallinity and morphology of nanocrystals influence significantly the PL emission, decreasing for nanodots and increasing for nanorods with the high aspect ratio. It also results in the variation in electronic structure from X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission (UPS) characterization that the valence band maximum shifts to low-energy level corresponding to the samples with aspect ratios of 3, 5, and 1, respectively